My primary interest is expression in computer programs: when I write a program, I want it to say what I mean, as simply and directly as possible. Many problems can be well expressed at present; I love finding better ways to express those that can't.

Some things I am doing or have done:

I used to co-teach 6.945 Large-scale Symbolic Systems (formerly 6.891, Adventures in Advanced Symbolic Programming) with Gerry Sussman. Gerry continues to teach the class, and he and I are writing a book based on some of the ideas explored in the class.

Gerry and I co-developed a new programming language that supports pervasive meta-data annotation and efficient dependency-directed backtracking. While the design is done and there's a working prototype, work has temporarily stopped due to lack of time. The book will probably use this language at some point to I expect further development then.

I maintain the MIT/GNU Scheme system, although most of the work these days is done by others.

I used to work on the TAMI project, developing technology to help organizations track data usage and its associated policy compliance, with the long-term goal of improving both privacy and security through accountability.

I used to maintain the archive of the ThinkPad mailing list. These days I primarily use a Chromebook Pixel.

I did some work on the Intelligent Book project. We taught Intelligent Tutoring Systems in Spring 2005 and an alternative Circuits class in Spring 2004.

I like a few outdoor activities: bicycling, hiking, camping, and skiing. I commute to and from work using a Stromer ST2, an amazing and super-fun e-bike.

I'm a ham radio operator with call sign K8SH; I was active in NTS and was the net manager for 1RN/3 and the EMRI CW net until early 2008. I don't have a station set up right now but will probably set one up in the next few years.

My favorite musical groups are The Grateful Dead and Phish; I've been downloading live music from etree.org and buying music from LivePhish.

I was looking down at the continent, in an idle nonfocussed way, remembering the other guises and transformations I had seen it in, when the Canopean Crystal floated down and lay in the air in front of me. It was in its most usual shape, a cone, and as it hung point down among the charming clouds of that atmosphere, with the blue of the atmosphere beyond, it was most attractive, and I was admiring it when it moved off, slowly, and I followed. I did not understand this lesson, which I assumed it was, but only watched, and enjoyed --- as always --- the aesthetic bonuses of this planet. The Crystal became a tetrahedron --- the three facets of it I could see reflecting the landscape of these blue and white skies --- then a globe. A glistening ball rolled and danced among the clouds. I was laughing with the pleasure of it, and even clapping my hands and applauding ... it elongated and became like a drop of liquid at the moment when it falls from a point. But it was lying horizontally, the thin end in front of us. This exquisite drop of crystalline glitter was thus because of the pressures of the atmosphere, it was adjusting itself to the flow of the jet stream, we were being sped along by the air rivers, and the Crystal had become a long transparent streak. My craft was almost in the end of the streak, and for a few moments we seemed almost to intermingle, and what delicious thoughts sang through my mind as we saw the rivers and mountains and deserts of the landmass beneath through what seemed like liquefied light. My guide was changing again, was showing how it had to change, and flow, and adapt itself, for all the movements and alterations of the atmosphere we were submerged in like liquid moulded this Globe, or Rod, or Streak, or Fringe.... How many shapes it assumed, this enchanting guide of mine, as we followed the flowing streams of the upper airs of Rohanda --- how it evolved and adapted and shone! --- but then dulled, so it seemed as if a lump of dullish lead lay there, sullen in a chilly and yellow light, but then lost its grey, and took in a sparkle and a glisten again, and seemed to frolic and to play, and yet again became serious and stern, with an edge of hardness in it, all the time a flowing and an answering, and an astonishment, but then, my mind lost in contemplation of this Crystal that seemed to have become no more than a visible expression of the air currents, I saw it had stopped, and had become the shape of a drop that points down. [...]

[...] But still it hovered there, silent, changing its shape at every moment, demonstrating the possibilities of a fluid communication ... and then it was lifting up and away, was a great drop of glittering water from the black depths of space, and it hung there, this infinitely various and variable and flowing thing, this creation of the Canopean mind, it spoke to me, it sang to me, it sent messages of hope, of the eternal renewal of everything, and then it again elongated itself, and ebbed up and fled back to its station high above Rohanda, where it was a mote in sunlight, a memory of itself.